U.S. Patent Application Publication No. US 2007/0131918, published Jun. 14, 2007, relates to an impact head for a guardrail including cable routing means adapted to form a tortuous or convoluted path through which a cable is threaded. The convoluted path that the cable must follow through the impact head of the invention restricts movement of the cable through the head, thereby providing sufficient friction to slow down the movement of the impact head during a vehicle impact.
The above-identified U.S. patent application Publication discusses existing highway guardrail end treatment systems and deficiencies of such systems that the guardrail disclosed in the U.S. patent application Publication addresses.
As noted in the U.S. Patent Publication No. U.S. 2007/0131918, existing highway guardrail end treatment systems include the breakaway cable terminal (BCT), the eccentric loader terminal (ELT), the modified eccentric loader terminal (MELT), the vehicle attenuating terminal (VAT), the extruder terminal (ET 2000 and ET plus), the slotted rail terminal (SRT), the sequential kinking terminal (SKT) and the flared energy absorbing terminal (FLEAT).
Terminal ends (the ends facing oncoming traffic) generally consist of one or more guardrails having a W-shaped cross-section supported by a series of both controlled release terminal (CRT) or frangible posts and standard highway guardrail posts. A cable assembly arrangement may be utilized to anchor the end of the rail to the ground, transferring tensile load developed in a side-on impact by a vehicle to the ground anchor. Generally, the terminal ends have an impact head arrangement that will be the first structural member impacted by an errant vehicle during an end-on impact which is designed to spread or absorb some of the impact energy.
Some terminal ends (such as the ET, SKT and FLEAT) absorb the energy of the impacting vehicle during an end-on or head-on impact by having an impact head that slides down the W-shaped guardrails and breaks away the support posts as it travels down the rails. All of the other above-mentioned terminal ends work on the principal of various weakening devices in the posts and rails to allow an errant vehicle to penetrate the terminal end in a controlled manner and prevent the rails from spearing the vehicle or the vehicle from vaulting or jumping over a relatively stiff terminal end.
As indicated in the above-identified U.S. patent application Publication, all of the above-mentioned guardrail terminal ends are considered to be gating. That is, if the guardrail terminal ends are impacted between the impact head and the “length of need” (where the “length of need” is considered to be the distance from the terminal end to where the guardrail will direct a vehicle during an angled impact) during an angled impact, the terminal end will gate and allow the impacting vehicle to pass through the backside of the terminal end. However this gating effect may have undesirable or unsafe results. As noted above, the guardrail disclosed in the patent application publication 2007/0131918 addresses these problems.
These problems are also addressed by the crash attenuator apparatus disclosed and claimed herein, the apparatus incorporating a number of novel structural elements which cooperate in a unique manner to provide the desired results. The apparatus effectively absorbs and distributes forces caused by vehicular impact whether the vehicle strikes an end of the apparatus head-on or crashes into a side of the apparatus. It can also be utilized to protect or shield errant vehicles from roadside hazards, guardrail and barrier terminals, etc.
U.S. Pat. No. 5,022,782 discloses a vehicle crash barrier in which a wire cable extends along an elongated, collapsible frame. The wire cable extends generally parallel to the frame. Friction brakes are mounted on a front section of the frame to decelerate a vehicle axially striking the frame at the front section. U.S. Pat. No. 5,022,782 does not disclose the advantageous features described and claimed herein.